Frame for forming image forming apparatus and manufacturing method of the frame

ABSTRACT

A frame for forming an image forming apparatus for forming an image on a recording material includes a first stay, including a supporting portion for supporting the frame relative to an installation surface, for forming a bottom of the frame; a second stay, including a supporting portion for supporting the frame relative to the installation surface, for forming the bottom of the frame; a post to which the first stay and the second stay are secured; and a positioning portion, provided as a part of the post, for positioning the first stay and the second stay with respect to a horizontal plane direction. The first stay and the second stay are fixed to the post by welding.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a frame for forming an image formingapparatus such as a printer, a facsimile machine, a copying machine or amulti-function machine having a plurality of functions of thesemachines, and relates to a manufacturing method of the frame.

As a frame (structure) for forming the image forming apparatus, astructure in which a bottom plate is provided at a bottom of a mainassembly frame in which an image forming portion is provided has beenconventionally known. Further, a so-called three-point supportingstructure in which a supporting portion for supporting the image formingapparatus is provided at three positions of the bottom plate has alsobeen known (for example, Japanese Laid-Open Patent Application2013-156569).

However, as described above, in the case where the frame for the imageforming apparatus is constituted by providing the bottom plate at thebottom of the main assembly frame, a cost increases. For this reason, itwould be considered that the bottom of the frame is constituted by usinga plurality of stays in combination. However, in the case where thebottom is constituted by the plurality of stays and supporting portionsare provided on separate stays, positional accuracy of the supportingportions provided at a plurality of positions lowers due to a mountingtolerance of the stays relative to the main assembly frame or a mountingtolerance of the supporting portions relative to the stays. That is, asin the conventional frame, in the case where the bottom is constitutedby a single bottom left, such a tolerance is small, but in the casewhere the bottom is constituted by the plurality of stays, a variationis liable to generate in positional relationship among the respectivestays or in positional relationship among the supporting portionsprovided on the stays. Further, when a degree of the variation inpositional relationship among the supporting portions with respect to anup-down direction is large, even when an installation surface is flat,there is a possibility that an installed image forming apparatus leans.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of theabove-described circumstances so as to realize a frame for an imageforming apparatus and a manufacturing method of the frame which arecapable of suppressing a variation in positional relationship amongsupporting portions with respect to an up-down direction even when abottom of the image forming apparatus is constituted by a plurality ofstays.

A principal object of the present invention is to enhance mountingaccuracy of the plurality of stays forming the bottom.

According to an aspect of the present invention, there is provided aframe for forming an image forming apparatus for forming an image on arecording material, the frame comprising: a first stay, including asupporting portion for supporting the frame relative to an installationsurface, for forming a bottom of the frame; a second stay, including asupporting portion for supporting the frame relative to the installationsurface, for forming the bottom of the frame; a post to which the firststay and the second stay are secured; and a positioning portion,provided as a part of the post, for positioning the first stay and thesecond stay with respect to a horizontal plane direction, wherein thefirst stay and the second stay are fixed to the post by welding.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of an image forming apparatus and a sheetfeeding unit in First Embodiment.

FIG. 2 is a schematic view of the image forming apparatus in the FirstEmbodiment.

In FIG. 3, (a) is a perspective view of a frame (structure) for theimage forming apparatus as seen from above in a front side, and (b) is aperspective view of the frame for the image forming apparatus as seenfrom above in a rear side, in the First Embodiment.

FIG. 4 is a perspective view of the frame for the image formingapparatus as seen from below in the First Embodiment.

In FIG. 5, (a) is a perspective view of a lower front stay, and (b) is asectional view of the lower front stay, in the First Embodiment.

In FIG. 6, (a) is a perspective view of a rear bottom stay, and (b) is asectional view of the rear bottom stay, in the First Embodiment.

In FIG. 7, (a) is a perspective view of a lower left stay, (b) is anenlarged view of an α portion in (a) of FIG. 7, and (c) is a sectionalview of the lower left stay, in the First Embodiment.

In FIG. 8, (a) is a perspective view of a connecting portion between thelower front stay and a rear-side post as seen from above, and (b) is aperspective view of a connecting portion between the lower front stayand the rear-side post as seen from below, in the First Embodiment.

FIG. 9 is a perspective view of a connecting portion between the lowerfront stay and a left-side post as seen from above in the FirstEmbodiment.

In FIG. 10, (a) is a perspective view of a connecting portion betweenthe rear bottom stay and a left-side plate as seen from a rear side, and(b) is a perspective view of the connecting portion between the rearbottom stay and the left-side plate as seen from a front side, in theFirst Embodiment.

In FIG. 11, (a) is a perspective view of a positioning jig as seen fromabove, and (b) is a perspective view of the positioning jig as seen fromabove with an angle different from an angle in (a) of FIG. 11, in theFirst Embodiment.

FIG. 12 is a perspective view of a state in which the frame for theimage forming apparatus is disposed on the positioning jig, as seen fromabove in the First Embodiment.

In FIG. 13, (a) is a perspective view of a lower left stay, (b) is anenlarged view of a β portion in (a) of FIG. 13, and (c) is a perspectiveview of the lower left stay, in Second Embodiment.

FIG. 14 is a perspective view of a connecting portion between the lowerleft stay and a left-side post as seen from above in the SecondEmbodiment.

FIG. 15 is a perspective view of a connecting portion among the lowerleft stay, a rear-side plate and a rear bottom plate as seen from abovein the Second Embodiment.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

First Embodiment of the present invention will be described using FIGS.1 to 12. First, a general structure of an image forming apparatus inthis embodiment will be described using FIGS. 1 and 2.

[Image Forming Apparatus]

An image forming apparatus 100 in this embodiment is a full-colorprinter employing an electrophotographic type. Such an image formingapparatus 100 is mountable on an upper surface (mounting surface) of anoptional sheet (paper) feeding module 150 as shown in FIG. 1. The imageforming apparatus 100 and the optional sheet feeding module 150 includetwo-stage sheet feeding cassette 101 a, 101 b and two-stage sheetfeeding cassettes 151 a, 151 b, respectively. The respective sheetfeeding cassettes accommodate recording materials (sheet materials suchas sheets (papers) and OHP sheets) different in size and basis weight.It is possible to select the recording material to be used, through anoperating portion 102 of the image forming apparatus 100 or an externalterminal such as a personal computer connected with the image formingapparatus 100. In the following description, a side where a useroperates the image forming apparatus 100 is referred to as a front side,and a back (rear) surface side of the image forming apparatus 100 isreferred to as a rear surface. Left and right of the image formingapparatus 100 are those as seen from the front side.

The image forming apparatus 100 includes an image forming portion 103for forming a toner image and a recording material feeding portion 104for feeding a recording material onto which the toner image formed bythe image forming portion 103 is transferred. The image forming portion103 has a constituting of a so-called tandem type in which a pluralityof process cartridges 105 as a plurality of image forming stations arearranged in a travelling direction of an intermediary transfer belt 106.At the image forming stations, toner images of yellow, magenta, cyan andblack are formed, respectively.

In the image forming apparatus 100 in this embodiment as describedabove, the plurality (4 in this embodiment) of process cartridges 105are detachably mounted to an apparatus main assembly 120. The respectiveprocess cartridges 105 have the same constitution, and therefore in thefollowing, a leftmost process cartridge 105 will be described, and otherprocess cartridges will be omitted from illustration of referencenumerals or symbols and omitted from description.

The process cartridge 105 includes a photosensitive drum 107 which is adrum-shaped electrophotographic photosensitive member as an imagebearing member, a charging roller 108, a developing device 109 and adrum cleaner 110. The photosensitive drum 107 is rotationally driven ata predetermined process speed by an unshown drum motor. A surface of thephotosensitive drum 107 is electrically charged uniformly by thecharging roller 108 as a charging means. The charged surface of thephotosensitive drum 107 is irradiated with a laser beam on the basis ofimage information by an exposure device 111 as an imaging portion(exposure means), so that an electrostatic latent image is formed. Theelectrostatic latent image on the photosensitive drum 107 is developedas a developer image (toner image) by deposition of a toner by thedeveloping device 109. The toner image on the photosensitive drum 107 isprimary-transferred onto the intermediary transfer belt 106 as anintermediary transfer member by applying a primary transfer bias tobetween a primary transfer roller 112 as a primary transfer means andthe photosensitive drum 107. A transfer residual toner remaining on thephotosensitive drum 107 after the transfer is removed by the drumcleaner 110.

The above-described steps are executed in the respective processcartridges 105, so that the respective color toner images formed on thephotosensitive drums 107 of the process cartridges 105 are superposedlytransferred onto the intermediary transfer belt 106. Thus, a full-colortoner images is formed on the intermediary transfer belt 106. The tonerimage on the intermediary transfer belt 106 is secondary-transferredonto the recording material fed, by the recording material feedingportion 104 described later, to a secondary transfer portion formed bythe intermediary transfer belt 106 and a secondary transfer roller 113as a secondary transfer means. The toner remaining on the intermediarytransfer belt 106 after the transfer is removed by a belt cleaner 114.

The recording material feeding portion 104 is constituted by a pluralityof feeding rollers, and picks up the recording material accommodated inthe associated one of the sheet feeding cassettes 101 a, 101 b, 151 a,151 b and then feeds the recording material to the secondary transferportion. The feeding of the recording material to the secondary transferportion is performed by being timed to the toner image on theintermediary transfer belt 106 by a registration roller pair 115. In anexample shown in FIG. 2, the recording material is fed from theassociated one of the sheet feeding cassettes 101 a, 101 b disposed at alower portion of the apparatus main assembly, toward an upper portion ofthe apparatus main assembly. For this purpose, the recording materialfeeding portion 104 is disposed along a substantially up-down direction(vertical direction) in one side (right side as seen from the front sideof the image forming apparatus) of the apparatus main assembly.

The recording material on which the toner image is transferred at thesecondary transfer portion is heated and pressed by a fixing device 116,so that the toner image is fixed. The recording material on which thetoner image is fixed is discharged on a discharge tray 117.

Here, as described above, in the image forming apparatus 100, imageformation and feeding of the recording material are effected. For thisreason, when a frame structure (frame) of the image forming apparatus100 is distorted, an image defect and an improper operation generate insome cases. On the other hand, in the optional sheet feeding module 150,even when the frame is somewhat distorted, the distorted frame has noinfluence on a function of feeding the recording material and deliveringthe recording material to the image forming apparatus. Accordingly,suppression of distortion of the frame structure of the image formingapparatus 100 is important for the purpose of suppressing the imagedefect and the improper operation.

[Frame Structure]

A frame structure 130 as an image forming apparatus frame (structure)constituting the apparatus main assembly 120 will be described usingFIGS. 3 and 4. The frame structure 130 includes a main assembly frame200 and a bottom (portion) 300. Inside the main assembly frame 200, theimage forming portion 103 and the recording material feeding portion 104which are as described above are disposed. The bottom 300 is disposed ata lower position of the main assembly frame 200 with respect to theup-down direction (vertical direction) and in the neighborhood of aninstallation surface (mounting surface). First, a constitution of themain assembly frame 200 will be described.

[Main Assembly Frame]

The main assembly frame 200 is constituted by connecting, as a pluralityof frame members disposed with respect to the up-down direction, afront-side plate 201, a rear-side plate 202 (side plate), a left-sidepost 205 (first post) and a right-side post 204 (second post) viavarious stays and side plates. First, the front-side plate 201 and therear-side plate 202 are connected by main bases 203 a, 203 b to whichthe exposure device 111 is to be mounted. The front-side plate 201 isconnected to end supported by the right-side post 204 at a right endthereof and is connected to and supported by the left-side post 205 at aleft end thereof. The rear-side plate 202 is constituted by a side plateportion 202 a disposed with respect to the up-down direction, and anupper plate portion 202 b, a right plate portion 202 c and a left plateportion 202 d which are provided so as to project from an upper end, aright end and a left end, respectively, of the side plate portion 202 a.In a space defined by these plate portions 202 a to 202 d, variouselectrical components such as a motor for driving the image formingapparatus 200 are to be disposed.

The right-side post 204 is disposed so as to extend to the neighborhoodof the installation surface in a downward direction and includes a firstside wall 204 a and a second side wall 204 b which are parallel withrespect to the up-down direction and which are perpendicular to eachother. The left-side post 205 is disposed so as to extend to theneighborhood of the installation surface in a downward direction andincludes a first side wall 205 a and a second side wall 205 b which areparallel with respect to the up-down direction and which areperpendicular to each other. The first side walls 204 a, 205 a aredisposed opposed to each other so that wall surfaces thereof areperpendicular to a left-right direction, and the second side walls 204b, 205 b are disposed so that wall surfaces thereof are perpendicular tothe front-rear direction and oppose the rear-side plate 202 and so thatthe second side walls 204 b, 205 b are in the same plane parallel to theleft-right direction.

In the neighborhood of the installation surface between the right-sidepost 204 and the rear-side plate 202, the post 204 and the plate 202 areconnected by lower right stays 206 a, 206 b. The lower right stays 206a, 206 b are provided with rails for not only regulating positions ofthe right-side post 204 and the rear-side plate 202 with respect to thefront-rear direction but also taking the sheet feeding cassettes 101 a,101 b in and out. The lower right stays 206 a, 206 b are disposed inside(leftward) the first side wall 204 a of the right-side post 204 toensure a space in which the recording material fed from theabove-described optional sheet feeding module 150 to the recordingmaterial feeding portion 104.

In the neighborhood of the installation surface between the left-sidepost 205 and the rear-side plate 202, the post 204 and the plate 202 areconnected by lower left side plates 207 a, 207 b. The lower left sideplates 207 a, 2067 are disposed at positions opposing the lower rightstays 206 a, 206 b and are provided with rails for not only regulatingpositions of the left-side post 205 and the rear-side plate 202 withrespect to the front-rear direction but also taking the sheet feedingcassettes 101 a, 101 b in and out. Accordingly, the sheet feedingcassettes 101 a, 101 b are mountable in and demountable from theapparatus main assembly 120 by the rails provided on the lower rightstays 106 a, 106 b and the lower left side plates 207 a, 207 b.

The right-side post 204 and the rear-side plate 202 are connected at anupper end by an upper right stay 208 and connected at an intermediaryportion with respect to the up-down direction by an intermediary rightstay 209. The left-side post 205 and the rear-side plate 202 areconnected at an upper end by an upper left stay 210 and connected at anintermediary portion with respect to the up-down direction by anintermediary left stay 211. These stays 208 to 211 regulate positions ofthe right-side post 204, the left-side post 205 and the rear-side plate202 with respect to the front-rear direction.

The respective posts, stays, side plates and the like which constitutethe main assembly frame 200 as described above are connected to eachother by connecting members such as screws or by welding or the like. Byemploying such a constitution, between the front-side plate 201 and thebottom 300, a lower front opening A through which the two-stage sheetfeeding cassettes 101 a, 101 b are mountable and demountable isprovided. Further, as described above, the recording material feedingportion 104 is disposed in the right side, and therefore in the casewhere the recording material jammed at the recording material feedingportion 104 is removed or in the like case, a right surface opening Bthrough which the user has access to the inside of the image formingapparatus 100 is provided.

[Bottom (Portion)]

A structure of the bottom (portion) 300 will be described. The bottom300 is constituted by a plurality of stays 301 (first stay), 303 (secondstay), 302 (third stay) fixed at a lower portion of the main assemblyframe 200. These stays 301, 303, 302 are provided with three supportingportions 311 (first supporting portion), 313 (second supportingportion), 312 (third supporting portion) for supporting the imageforming apparatus 100 relative to the installation surface. In the caseof this embodiment, the installation surface of the image formingapparatus 100 is the upper surface of the sheet feeding module 150, butin the case where the image forming apparatus 100 is disposed directlyon a floor surface, the floor surface is the installation surface. Inthis embodiment, a so-called 3-point supporting structure in which theimage forming apparatus 100 is supported by the three supportingportions 311, 312, 313 only.

Of the plurality of stays, the lower front stay 301 as the first stay isprovided with the first supporting portion 311 of the three supportingportions. Of the plurality of stays, the rear bottom stay 302 as thethird stay is provided with the third supporting portion 312 of thethree supporting portions. Of the plurality of stays, the lower leftstay 303 as the second stay is provided with the second supportingportion 313 of the three supporting portions. A positional relationshipamong the first to third stays is not limited thereto, but may also beany combination of the stays with the supporting portions. In thisembodiment, the lower front stay 301 as the first stay is disposed inthe neighborhood of the installation surface between the right-side post204 and the left-side post 205, so that positions of these posts areregulated with respect to a widthwise direction (left-right direction).The rear bottom stay 302 as the third stay is disposed at the bottom ofthe rear-side plate 202, so that a bottom of the main assembly frame ata rear portion is formed. The lower left stay 303 as the second stayconnects the left-side post 205 and the rear bottom stay 302 in theneighborhood of the installation surface.

[Arrangement of Supporting Portions]

Arrangement positions of the three supporting portions 311, 312, 313will be described using FIG. 4. First, the first supporting portion 311and the third supporting portion 312 are provided in the neighborhood ofa right front corner and a right rear corner, respectively, of thebottom 300 so as to sandwich the recording material feeding portion 104(FIG. 2). The second

supporting portion 313 is disposed in the neighborhood of a left endcenter of the bottom 300 so that the center of gravity G of the imageforming apparatus 100 is positioned inside a line (broken line) Lconnecting the three supporting portions 311, 312, 313.

As described above, the various electrical components such as thedriving portion which is a heavy object, and an electrical portion aredisposed on the rear-side plate 202 constituting a rear side of theimage forming apparatus 100. The recording material feeding portion 104is disposed in the right side of the image forming apparatus 100. Forthis reason, the position of the center of gravity G is positioned in aright rear side of a center of the image forming apparatus 100. That is,the center of gravity G of the image forming apparatus 100 is in aposition closest to the right-rear-side third supporting portion 312 ofthe three supporting portions 311, 312, 313. In the case where the imageforming apparatus 100 is installed alone on the installation surface,the supporting portions 311, 312, 313 disposed at three positionscontact the installation surface, and therefore an attitude of the imageforming apparatus 100 is uniquely determined by heights of the threesupporting portions 311, 312, 313. Therefore, by supporting the imageforming apparatus 100 at the 3 positions (points), even in the casewhere a degree of flatness of the installation surface of the imageforming apparatus 100 is low, twisting and distortion of the imageforming apparatus 100 can be suppressed.

[Stays Constituting Bottom]

A structure of each of the 3 stays 301, 302, 303 constituting the bottom300 will be described. First, the lower front stay 301 disposed in thefront side of the image forming apparatus 100 will be described using(a) and (b) of FIG. 5. The lower front stay 301 is constituted by acombination of a first plate member 301 a and a second plate member 301b each formed by subjecting a metal plate to bending. As shown in (b) ofFIG. 5, the first plate member 301 a is formed by being bent in asubstantially crank shape at each of end portions with respect to thewidthwise direction perpendicular to a longitudinal direction. Thesecond plate portion 301 b is formed by being bent in one direction ateach of the widthwise end portions. Then, the first plate portion 301 aand the second plate portion 301 b are combined so as to form a closedcross-section as shown in (b) of FIG. 5, and are connected with eachother by welding. By constituting the lower front stay 301 so as to formthe closed cross-section, geometrical moment of inertia can be madelarge, so that a degree of deformation of the image forming apparatus100 due to the weight of the image forming apparatus 100 can beremarkably suppressed.

By subjecting the second plate member 301 b disposed in a lower surfaceside of the lower front stay 301 to drawing, the first supportingportion 311 is formed integrally with the lower front stay 301. That is,as shown in (a) of FIG. 5, a part of the longitudinal end portion of thesecond plate member 301 b is subjected to the drawing so as to be pushedout downward, so that at a lower surface of the second plate member 301b, the first supporting portion 311 projecting downward more thananother portion is formed.

Next, the rear bottom stay 302 disposed in the rear side of the imageforming apparatus 100 will be described using (a) and (b) of FIG. 6. Therear bottom stay 302 is constituted by a combination of a first platemember 302 a and a second plate member 302 b each formed by subjecting ametal plate to bending. As shown in (b) of FIG. 6, the first platemember 302 a is formed by being not only depressed at an intermediaryportion but also bent in one direction at each of end portions withrespect to the widthwise direction perpendicular to a longitudinaldirection. The second plate portion 302 b is formed by being bent in asubstantially crank shape at each of the widthwise end portions. Onewidthwise end portion as the front-side portion of the second platemember 302 b in a disposed state of the second plate member 302 bdisposed in a lower surface side of the rear bottom stay 302 constitutesa projected plate portion 302 c projected upward more than the firstplate member 302 a disposed in an upper surface side in a state in whichthe first plate member 302 a and the second plate member 302 b aredisposed in combination. Then, the first plate portion 302 a and thesecond plate portion 302 b are combined so as to form a closedcross-section as shown in (b) of FIG. 6, and are connected with eachother by welding.

By subjecting the second plate member 302 b disposed in a lower surfaceside of the rear bottom stay 302 to drawing, the third supportingportion 312 is formed integrally with the rear bottom stay 302. That is,as shown in (a) of FIG. 6, a part of the longitudinal end portion of thesecond plate member 302 b is subjected to the drawing so as to be pushedout downward, so that at a lower surface of the second plate member 302b, the third supporting portion 312 projecting downward more thananother portion is formed.

Next, the lower left stay 303 disposed in the left side of the imageforming apparatus 100 will be described using (a), (b) and (c) of FIG.7. The lower left stay 303 is constituted by a combination of a firstplate member 303 a and a second plate member 303 b each formed bysubjecting a metal plate to bending. As shown in (c) of FIG. 7, thefirst plate member 303 a is formed by being not only depressed at anintermediary portion but also bent in one direction at each of endportions with respect to the widthwise direction perpendicular to alongitudinal direction. The second plate portion 303 b is formed bybeing bent in one direction at one widthwise end portion and by beingbent in a substantially crank shape at the other widthwise end portion.Then, the first plate portion 303 a and the second plate portion 303 bare combined so as to form a closed cross-section as shown in (c) ofFIG. 7, and are connected with each other by welding.

The second supporting portion is constituted separately from the lowerleft stay 303 and is fixed to the lower left stay 303. In a state inwhich the second supporting portion 313 is not fixed to the lower leftstay 303 but is positioned with respect to an in-plane directionperpendicular to the up-down direction, the second supporting portion313 is disposed movably in the up-down direction. In the case of thisembodiment, the lower left stay 303 is disposed along the front-reardirection, and therefore the second supporting portion 313 is disposedmovably in the front-rear direction in a state in which the secondsupporting portion 313 is positioned relative to the lower left stay 303with respect to the front-rear direction and the left-right direction.

Specifically, the lower left stay 303 includes a pair of side surfaces303 c, 303 d which are parallel to the up-down direction and which areparallel to each other. The side surface 303 c in one side is an outsidesurface of the bent portion formed by bending the first plate member 303a at one widthwise end portion, and the other side surface 303 d is anoutside surface of the bent portion formed by bending the second platemember 303 b at the other widthwise end portion.

The second supporting portion 313 includes a pair of side wall portions313 a, 313 b, a connecting portion 313 c and a contact portion 313 d.The pair of side wall portions 313 a, 313 b are disposed opposed to thepair of side surfaces 303 c, 303 d, respectively. The connecting portion313 c connects lower end portions of the pair of the side wall portions313 a, 313 b. The contact portion 313 d is provided on the connectingportion 313 c and is contacted to the installation surface. Thethus-constituted second supporting portion 313 includes the pair of sidewall portions 313 a, 313 b and the connecting portion 313 c each formedby bending the metal plate. By subjecting the connecting portion 313 cto the drawing, the contact portion 313 d is formed integrally with theconnecting portion 313 d. That is, as shown in (c) of FIG. 7, a part ofthe connecting portion 313 c is subjected to the drawing so as to bepushed out downward, so that at a lower surface of the connectingportion 313 c, the contact portion 313 d projecting downward more thananother portion is formed.

The above-described first supporting portion 311 and the thirdsupporting portion 312 are formed so that each of contact surfaces withthe installation surface has a substantially circular shape. On theother hand, the contact portion 313 d constituting the second supportingportion 313 is formed so that an area of the contact surface thereof islarger than an area of each of the contact surfaces of the firstsupporting portion 311 and the third supporting portion 312.Specifically, the contact surface of the contact portion 313 d has sucha shape that end portions of a flat surface extending in the front-reardirection which is an arrangement direction of the lower left stay 303are formed in an arcuate shape. This is because the two supportingportions 311, 312 are disposed in the right side of the image formingapparatus 100 and on the other hand, only one supporting portion 313 isdisposed in the left side of the image forming apparatus 100. That is,an installation area in a side where the single supporting portion isdisposed is made large, so that stability of the image forming apparatus100 relative to the installation surface is improved. As a result, forexample, even in the case where such an external force that the userputs his (her) weight on the image forming apparatus 100 acts on theimage forming apparatus 100, it is possible to prevent the image formingapparatus 100 from leaning with reliability.

The lower left stay 303 includes a projected portion 303 e as anengaging portion as shown in (b) of FIG. 7. The projected portion 303 eis formed so as to project from each of the pair of side surfaces 303 c,303 d. On the other hand, the second supporting portion 313 is providedwith a cut-away portion 313 e as a portion-to-be-engaged engaging withthe projected portion 303 e. The cut-away portion 313 e is formed ineach of the pair of side wall portions 313 a, 313 b and is cut away fromeach of upper end portions of the side wall portions 313 a, 313 b withrespect to the up-down direction, so that the projected portion 303 ecan enter the cut-away portion 313 e.

Assembling of the second supporting portion 313 with the lower left stay303 is made in the following manner. First, the second supportingportion 313 is disposed so that the pair of side wall portions 313 a,313 b sandwich the pair of side surfaces 303 c, 303 d of the lower leftstay 303 and so that the cut-away portion 313 e and the projectedportion 303 e are aligned with each other. Then, the second supportingportion 313 is moved in an upward direction relative to the lower leftstay 303, so that not only the projected portion 303 e enters thecut-away portion 313 e but also the pair of side wall portions 313 a,313 b oppose the pair of side surfaces 303 c, 303 d, respectively. As aresult, the second supporting portion 313 is positioned relative to thelower left stay 303 with respect to the in-plane direction in a state inwhich the second supporting portion 313 is not fixed to the lower leftstay 303. In this embodiment, a stay-side positioning portion 320(positioning portion) is constituted by the pair of side surfaces 303 c,303 d, the pair of side wall portions 313 a, 313 b, the projectedportion 303 e and the cut-away portion 313 e.

That is, the pair of side wall portions 313 a, 313 b and the pair ofside surfaces 303 c, 303 d are contacted to or close to each other, thesecond supporting portion 313 is positioned relative to the lower leftstay 313 with respect to a direction (left-right direction), of thein-plane direction, perpendicular to the pair of side surfaces 303 c,303 d. Further, by engagement between the cut-away portion 313 e and theprojected portion 303 e, the second supporting portion 313 is positionedrelative to the lower left stay 313 with respect to a direction(front-rear direction), of the in-plane direction, parallel to the pairof side surfaces 303 c, 303 d. At this time, the projected portion 303 eis movable relative to the cut-away portion 313 e in the up-downdirection, and therefore the second supporting portion 313 is movablerelative to the lower left stay 303 in the up-down direction in a statein which the second supporting portion 313 is positioned with respect tothe front-rear direction and the left-right direction. The secondsupporting portion 313 is fixed to the lower left stay 303 by weldingafter positional adjustment (height adjustment) of the three supportingportions 311, 312, 313 with respect to the up-down direction is made asdescribed later.

[Positioning and Fastening of Stays to Main Assembly Frame]

Next, positioning and fastening of the above-described 3 stays 301, 302,303 to the main assembly frame 200 will be described using FIGS. 8 to 10while making reference to FIG. 4. The lower front stay 301 and the rearbottom stay 302 as the first stay and the third stay, respectively, aredisposed movably in the up-down direction in a state in which thesestays are not fixed to the main assembly frame 200 but are positionedrelative to the main assembly frame 200 with respect to the in-planedirection (horizontal plane direction) perpendicular to the up-downdirection. On the other hand, the lower left stay 303 as the second stayis, after being fixed to the main assembly frame 200 with respect to theup-down direction and the in-plane direction, disposed movably in theup-down direction in a state in which the second supporting portion 313is positioned relative to the lower left stay 303 with respect to thein-plane direction. Specific description will be made below.

First, the positioning and the fastening of the lower front stay 301will be described using FIGS. 8 and 9. In FIG. 8, (a) and (b) areperspective views each showing a state in which the lower front stay 301is positioned relative to the right-side post 204 and is fastened to theright-side post 204. The right-side post 204 includes, as describedabove, the first side wall 204 a and the second side wall 204 b whichare parallel to the up-down direction and which are perpendicular toeach other. The lower front stay 301 is disposed in contact with orclose to only the first side wall 204 a and the second side wall 204 bat a right end portion thereof. The first side wall 204 a is disposed inparallel to the front-rear direction, and the second side wall 204 b isdisposed in parallel to the left-right direction. For this reason, theright end portion of the lower front stay 301 is disposed movably in theup-down direction in a state in which the right end portion ispositioned by the first side wall 204 a and the second side wall 204 bwith respect to the front-rear direction and the left-right direction.In this embodiment, a first positioning portion 2040 is constituted bythe first side wall 204 a and the second side wall 204 b. That is, thefirst positioning portion 2040 positions the lower front stay 301 withrespect to the left-right direction (horizontal plane direction) butdoes not position the lower front stay 301 with respect to the up-downdirection (vertical direction). The right end portion of the lower frontstay is, as described later, fixed to the right-side post 204 atfastening portions 241 to 244 by welding after the positioned adjustment(height adjustment) of the three supporting portions 311, 312, 313 withrespect to the up-down direction.

FIG. 9 is a perspective view showing a state in which the lower frontstay 301 is positioned relative to the left-side post 205 and isfastened to the left-side post 205. The left-side post 205 includes, asdescribed above, the first side wall 205 a and the second side wall 205b which are parallel to the up-down direction and which areperpendicular to each other. The lower front stay 301 is disposed incontact with or close to only the first side wall 205 a and the secondside wall 205 b at a left end portion thereof. The first side wall 205 ais disposed in parallel to the front-rear direction, and the second sidewall 205 b is disposed in parallel to the left-right direction. For thisreason, the left end portion of the lower front stay 301 is disposedmovably in the up-down direction in a state in which the right endportion is positioned by the first side wall 205 a and the second sidewall 205 b with respect to the front-rear direction and the left-rightdirection (horizontal plane direction). In this embodiment, a secondpositioning portion 2050 is constituted by the first side wall 205 a andthe second side wall 205 b. The left end portion of the lower front stay301 is, as described later, fixed to the left-side post 205 at fasteningportions 251 to 254 by welding after the positioned adjustment (heightadjustment) of the three supporting portions 311, 312, 313 with respectto the up-down direction. That is, the second positioning portion 2050positions the lower front stay 301 with respect to the left-rightdirection (horizontal plane direction) but does not position the lowerfront stay 301 with respect to the up-down direction (verticaldirection). In this way, the lower front stay 301 is disposed movably inthe up-down direction in a state in which the lower front stay 301 ispositioned relative to the right-side post 204 and the left-side post205 with respect to the front-rear direction and the left-rightdirection, and after the height adjustment of the respective supportingportions, is fixed to the right-side post 204 and the left-side post 205by welding.

Next, the positioning and the fastening of the rear bottom stay 302 willbe described using FIG. 10. In FIG. 10, (a) and (b) are perspectiveviews each showing a state in which the rear bottom stay 302 ispositioned relative to the rear-side plate 202 and is fastened to therear-side plate 202. The right-side post 204 includes, as describedabove, the side plate portion 202 a, and the right plate portion 202 cand the left plate portion 202 d which are projected rearward from rightand left end portions, respectively, of the side plate portion 202 a.Here, the side plate portion 202 is disposed in parallel to theleft-right direction, and the right plate portion 202 c and the leftplate portion 202 d and disposed in parallel to the front-reardirection. Accordingly, each of a combination of the side plate portion202 a and the right plate portion 202 c and a combination of the sideplate portion 202 a and the left plate portion 202 d provides arelationship between the first side wall and the second side wall whichare perpendicular to each other. At a front-side end portion of the rearbottom stay 302, as described above, the projected plate portion 302 cis formed.

The rear bottom stay 302 is disposed in contact with or closely to onlythe right portion 202 c and the left plate portion 202 d of therear-side plate 202 at end portions thereof with respect to theleft-right direction. That is, the rear bottom stay 302 is disposed incontact with or closely to only the side plate portion 202 a, the rightplate portion 202 c and the left plate portion 202 d. For this reason,the rear bottom stay 302 is disposed movably in the up-down direction ina state in which the rear bottom stay 302 is positioned by the sideplate portion 202 a, the right plate portion 202 c and the left plateportion 202 d with respect to the front-rear direction and theleft-right direction (horizontal plane direction). In this embodiment, athird positioning portion 2020 is constituted by the side plate portion202 a and the left plate portion 202 d, and a fourth positioning portion2021 is constituted by the side plate portion 202 a and the right plateportion 202 c. That is, the third and fourth positioning portionsposition the rear bottom stay 302 with respect to the left-rightdirection (horizontal plane direction) but does not position the lowerfront stay 301 with respect to the up-down direction (verticaldirection). The rear bottom stay 302 is, as described later, fixed tothe rear-side plate 202 at fastening portions 221 to 228 by weldingafter the positioned adjustment (height adjustment) of the threesupporting portions 311, 312, 313 with respect to the up-down direction.

The lower left stay 303 is, as shown in FIG. 4, disposed on the uppersurfaces of the lower front stay 301 and the rear bottom stay 302 so asto extends onto the upper surfaces. In this state, a front end portionof the lower left stay 303 is disposed in contact with or closely to thefirst side wall 205 a and the second side wall 205 b of the left-sidepost 205. A rear end portion of the lower left stay 303 is disposed incontact with or closely to the left plate portion 202 d of the rear-sideplate 202 and the rear bottom stay 302. Accordingly, in this state, thelower left stay 303 is movable relative to the main assembly frame 200in the up-down direction in a state in which the lower left stay 303 ispositioned relative to the main assembly frame 200 with respect to thefront-rear direction and the left-right direction.

However, as described above, the second supporting portion 313 providedon the lower left stay 303 is constituted separately from the lower leftstay 303, and is movable relative to the lower left stay 303 in a statein which the second supporting portion 313 is positioned relative to thelower left stay 303 with respect to the front-rear direction and theleft-right direction. For this reason, in this embodiment, the lowerleft stay 303 is fixed by welding to the first side wall 205 a and thesecond side wall 205 b of the left-side post 205 at the front endportion thereof and to the side plate portion 202 a and the left plateportion 202 b of the rear-side plate 202 at the rear end portionthereof. Thereafter, the second supporting portion 313 is, as describedabove, disposed movably relative to the lower left stay 303 in theup-down direction in a state in which the second supporting portion 313is positioned relative to the lower left stay 303, and then is fixed tothe lower left stay 303 after the height adjustment of the respectivesupporting portions is made.

The lower left stay 303 is disposed above the lower front stay 301 andthe rear bottom stay 302. In this embodiment, as described above, thesecond supporting portion 313 provided on the lower left stay 303disposed above the lower front stay 301 and the rear bottom stay 302 isprepared as the separate member from the lower left stay 303. This isbecause the lower left stay 303 is positioned above the lower front stay301 and the rear bottom stay 302 and therefore a distance between thelower surface thereof and the installation surface is larger than thosein the cases of other stays. That is, in the case where the supportingportion for the lower left stay 303 is formed in a projected shape bysubjecting the metal plate to the drawing similarly as in the cases ofthe lower front stay 301 and the rear bottom stay 302, the supportingportion is not readily projected correspondingly to the above-describeddistance. Accordingly, as in this embodiment, the supporting portion isprepared as the separate member, so that even when the distance from theinstallation surface is large, the formation of the projected portioncan be easily made.

[Height Adjusting Method of Supporting Portions]

Next, a method of positional adjustment (height adjustment) of the threesupporting portions 311, 312, 313 with respect to the up-down directionwill be described using FIGS. 11 and 12. As described above, each of thelower front stay 301, the rear bottom stay 302 and the lower left stay303 is not provided with a positioning portion relative to the mainassembly frame 200 with respect to the up-down direction. Accordingly, apositioning jig 400 for positioning each of the stays with respect tothe up-down direction in order to adjust the height of each of thesupporting portions will be described using (a) and (b) of FIG. 11. Thepositioning jig 400 is prepared by disposing, on an upper surface of abase 401, receiving portions 402 a, 402 b, 402 c for the threesupporting portions 311, 312, 313. These receiving portions 402 a, 402b, 402 c are regulated so that their upper surfaces are positioned inthe same flat plane. On the upper surface of the base 401, a receivingportion 403 for the lower front stay 301 and a receiving portion 404 forthe rear bottom stay 302 are disposed. Further, two walls 405, 406 areprovided to stand from the upper surface of the base 401 with respect tothe vertical direction, and are provided with two through holes 405 a,405 b and two through holes 406 a, 406 b, respectively.

When the respective stays are welded to the main assembly frame 200, asshown in FIG. 12, the main assembly frame 200 is installed on thepositioning jig 400. The front-side plate 201 and the rear-side plate202 of the main assembly frame 200 are provided with through holes atpositions corresponding to the holes 405 a, 405 b, 406 a, 406 b. Whenthe main assembly frame 200 is installed on the positioning jig 400, notonly a supporting bar 410 is passed through the hole 405 a, theassociated through hole of the main assembly frame 200 and the hole 406a but also a supporting bar 411 is passed through the hole 405 b, theassociated through hole of the main assembly frame 200 and the hole 406b. As a result, the main assembly frame 200 is supported by thepositioning jib 400 via the supporting bars 410, 411. Then, therespective stays are disposed at predetermined positions as describedabove so that the three supporting portions 311, 312, 313 are mounted onthe receiving portions 402 a, 402 b, 402 c, respectively.

The first supporting portion 311 and the third supporting portion 312provided on the lower front stay 301 and the rear bottom stay 302,respectively, are disposed close to one end portions of the stays. Forthis reason, when the first supporting portion 311 and the thirdsupporting portion 312 are only mounted on the receiving portions 402 a,402 b, there is a possibility that the stays are disposed in an inclinedstate. Therefore, in this embodiment, on the upper surface of the base401, at opposite end portions to the receiving portions 402 a, 402 b ina region where the lower front stay 301 and the rear bottom stay 302 aredisposed, receiving portions 403, 404 for the lower front stay 301 andthe rear bottom stay 302 are provided. Heights of the receiving portions403, 404 are set in consideration of projection amounts of the firstsupporting portion 311 and the third supporting portion 312 from theassociated stays. Thus, the respective stays are horizontally disposedin a state in which the first supporting portion 311 and the thirdsupporting portion 312 are mounted on the receiving portions 402 a, 402b and the lower front stay 301 and the rear bottom stay 302 are mountedon the receiving portions 403, 404.

On the other hand, in this state, the lower left stay 303 is mounted onthe lower front stay 301 and the rear bottom stay 302. The secondsupporting portion 313 provided on the lower left stay 303 is mounted ona receiving portion 402 c in a state in which the second supportingportion 313 is disposed on the lower left stay 303 at a predeterminedposition as described above. At this time, the respective stays 301,302, 303 are movable relative to the main assembly frame 200 in theup-down direction in a state in which the second supporting portion 313is positioned relative to the lower left stay 303 with respect to thefront-rear direction and the left-right direction. For this reason, asdescribed above, relative positions of the respective members withrespect to the up-down direction are adjusted, so that the respectivesupporting portions 311, 312, 131 can be mounted on the receivingportions 402 a, 402 b, 402 c. Further, at this time, the respectivemembers are positioned with respect to the front-rear direction and theleft-right direction and are movable only in the up-down direction, andtherefore when a positioning operation is performed, the respectivemembers do not readily deviate with respect to the front-rear directionor the left-right direction or do not readily lean with respect to thehorizontal direction. Accordingly, the adjusting operation as describedabove is easily performed.

In this way, the supporting portions 311, 312, 313 are mounted on thereceiving portions 402 a, 402 b, 402 c, so that lower surfaces of thesupporting portions are positioned on the same flat plane. Then, in thisstate, the stays 301, 302, 303 are welded to the associated posts orside plates of the main assembly frame 200, so that the stays are fixedto the main assembly frame 200. Further, the second supporting portion313 is welded to the lower left stay 303, so that the second supportingportion 313 is fixed to the lower left stay 303. As a result, in a statein which the positioning of the supporting portions is made, the bottom300 is fixed to the main assembly frame 200, so that the frame structure130 is formed.

In summary, the frame structure 130 is manufactured by the followingmanufacturing method. First, the lower front stay 301 and the rearbottom stay 302 are disposed movably relative to the main assembly frame200 in the up-down direction in a state in which the stays 301, 302 arepositioned relative to the main assembly frame 200 with respect to thein-plane direction perpendicular to the up-down direction (first step).Then, at least one of the lower front stay 301 and the rear bottom stay302 are moved in the up-down direction, so that the positionaladjustment of the three supporting portions 311, 312, 313 is performed(second step). Finally, the lower front stay 301 and the rear bottomstay 302 are fixed to the main assembly frame (third step). In thisembodiment, in the first step, also the lower left stay 303 is disposedmovably relative to the main assembly frame 200 in a state in which thelower left stay 303 is positioned relative to the main assembly frame200 with respect to the in-plane direction perpendicular to the up-downdirection. In the second step, the second supporting portion 313 ismoved relative to the lower left stay 303 in the up-down direction. Inthe third step, the second supporting portion 313 is fixed to the lowerleft stay 303.

In this embodiment, the frame structure 130 is manufactured using thepositioning jig 400 as described above, so that the positioning of thesupporting portions 311, 312, 313 can be easily performed. Further, theinside unit (such as the process cartridge 105) of the image formingapparatus 100 is positioned by the front-side plate 201 and therear-side plate 202, and therefore the inside unit and a plane formed bythe supporting portions 311, 312, 313 can be made parallel to eachother. In actuality, a degree of parallelism of the process cartridge105 with the supporting portions 311, 312, 313 can be roughly suppressedto 0.5 or less although it varies depending on accuracy of the jig.

As described above, according to this embodiment, even when the bottom300 is constituted by the plurality of stays 301, 302, 303, a variationin positional relationship among the supporting portions 311, 312, 313with respect to the up-down direction can be suppressed. The lower frontstay 301 and the rear bottom stay 302 are movable relative to the mainassembly frame 200 in the up-down direction in a state in which thestays 301, 302 are not fixed to the main assembly frame 200 but arepositioned relative to the main assembly frame 200 with respect to thein-plane direction. For this reason, the lower front stay 301 and therear bottom stay 302 are moved in the up-down direction, so that theheight adjustment of the supporting portions 311, 312, 313 can beperformed. In this embodiment, the second supporting portion 313 ismovable in the up-down direction in a state in which the portion 313 ispositioned relative to the lower left stay 303 with respect to thein-plane direction. In either case, after the height adjustment of thesupporting portions 311, 312, 313 is performed, the stays or thesupporting portions are fixed to the main assembly frame or the stays,so that a variation in positional relationship among the supportingportions 311, 312, 313 with respect to the up-down direction can besuppressed.

When the image forming apparatus 100 is mounted on, e.g., a horizontalsurface of the floor as the installation surface, the inside unit ishorizontal with respect to the direction of gravity, so that a functionsuch as a toner feeding function subjected to the influence of thegravitation can be stabilized. Further, distortion of the framestructure 130 can be suppressed, so that not only stabilization of thefeeding of the recording material by the recording material feedingportion 104 can be realized but also the deviation in positionalrelationship among the members such as the photosensitive drum can besuppressed, and thus it is possible to suppress generation of an imagedefect, improper operation and the like.

Second Embodiment

Second Embodiment of the present invention will be described using FIGS.13 to 15. In the First Embodiment described above, the second supportingportion 313 provided on the lower left stay 303 was made movable in theup-down direction in the state in which the portion 313 was positionedwith respect to the front-rear direction and the left-right direction.On the other hand, in this embodiment, a second supporting portion 313Ais fixed to a lower left stay 303A in a state in which the portion 313Ais positioned also with respect to the up-down direction. Otherconstitutions and actions are similar to those in the First Embodimentdescribed above, and therefore redundant description and illustrationare omitted or simplified and in the following, a portion different fromthe First Embodiment will be principally described.

The lower left stay 303A is, similarly as in the First Embodiment,constituted by combining a first plate member 303Aa and a second platemember 303Ab each formed by subjecting a metal plate to bending. Thefirst plate member 303Aa and the second plate member 303Ab are similarto the first left member 303 a and the second plate member 303 b in theFirst Embodiment. Also a second supporting portion 313A in thisembodiment is constituted as a separate member from the lower left stay303 similarly as in the First Embodiment. However, the second supportingportion 313A is different from the second supporting portion 313 in theFirst Embodiment, and is fixed to a lower surface of the second platemember 303Ab constituting a lower surface side of the lower left stay303A as shown in (a), (b) and (c) of FIG. 13.

For this reason, the second supporting portion 313A is formed by bendingthe metal plate, and includes a pair of abutting portions 313Aa, 313Ab,a connecting portion 313Ac and a contact portion 313Ad. The pair ofabutting portions 313Aa, 313Ab are formed by being bent in one directionfrom ends of the connecting portion 313Ac with respect to thelongitudinal direction (arranging direction or front-rear direction ofthe lower left stay 303A) and then by bending free ends in a directionsubstantially parallel to the connecting portion 313Ac. Further, a partof the connecting portion 313Ac is subjected to drawing so as to bepushed out downward, so that the contact portion 313Ad projectingdownward more than other portion is formed on the lower surface of theconnecting portion 313Ac. The contact portion 313Ad is similar to thecontact portion 313 d in the First Embodiment.

The lower left stay 303 includes a projected portion 303A as an engagingportion as shown in (b) of FIG. 7. The projected portion 303A is formedso as to project from each of two positions of the lower surface of thesecond plate member 303Ab. On the other hand, the second supportingportion 313A is provided with a cut-away portion 313Ae and a hole 313Afas portions-to-be-engaged engaging with the projected portion 303Ae. Thecut-away portion 313Ae is cut away in the front-rear direction at thefree end of the abutting portion 313Aa, so that one projected portion303Ae can enter the cut-away portion 313Ae. The hole 313Af is formed bypenetrating through a part of a free end portion of the abutting portion313Ab, so that the other projected portion 303Ae can enter the hole313Af.

Assembling of the second supporting portion 313A with the lower leftstay 303A is made in the following manner. First, the pair of abuttingportions 313Aa, 313Ab are abutted against the surface of the secondplate member 303Ab while engaging the cut-away portion 313Ae and thehole 313Af with the projected portions 303Ae. By the engagement of thecut-away portion 313Ae and the hole 313Ap with the projected portions303Ae, the second supporting portion 313A is positioned relative to thelower left stay 303A with respect to the in-plane direction (front-reardirection and front-rear direction). Further, the pair of abuttingportions 313Aa, 313Ab are abutted against the surface of the secondplate member 303Ab, so that the second supporting portion 313A ispositioned relative to the lower left stay 303A with respect to theup-down direction. Then, in this state, the second supporting portion313A is fixed to the lower left stay 303A by welding.

In the case of this embodiment, the abutting portions 313Aa, 313Ab ofthe second supporting portion 313A are abutted against the surface ofthe second plate member 303Ab, and therefore a contact area between thesecond supporting portion 313A and the second stay 303A can besufficiently ensured. For this reason, when the image forming apparatus100 is installed on the installation surface, a deformation of thesecond supporting portion 313A due to a load exerted on the secondsupporting portion 313A can be suppressed.

In this embodiment, as described above, the second supporting portion313A is fixed to the lower left stay 303A in a state in which theportion 313A is positioned relative to the stay 303A with respect to theup-down direction in addition to the in-plane direction, and thereforethe height adjustment of the second supporting portion 313A is made bythe lower left stay 303A. Positioning and fastening of the lower leftstay 303A to the main assembly frame 200 will be described using FIGS.14 and 15.

The lower left stay 303A is, similarly as in the First Embodiment,mounted on the upper surfaces of the lower front stay 301 and the rearbottom stay 302 so as to extend onto the lower front stay 301 and therear bottom stay 302. In this state, the front end portion of the lowerleft stay 303A is, as shown in FIG. 14, disposed so as to contact orapproach the first side wall 205 a and the second side wall 205 b of theleft-side post 205. The rear end portion of the lower left stay 303A is,as shown in FIG. 15, disposed so as to contact or approach the leftplate portion 202 d of the rear-side plate 202 and the rear bottom stay302. The side plate portion 202 a of the rear-side plate 202 is providedwith the cut-away portion or the through hole through which the lowerleft stay 303A is passable, so that the rear end portion of the lowerleft stay 303A passes through the side plate portion 202 a to reach arear end edge portion of the rear bottom stay 302. The rear end portionof the lower left stay 303A is provided with a bent portion 303Ac bentfrom an end portion of the first plate member 303Aa, so that an insidesurface of the bent portion 303Ac contacts the rear end edge portion ofthe rear bottom stay 302. As a result, the lower left stay 303A ismovable relative to the main assembly frame 200 in the up-down directionin a state in which the stay 303A is positioned relative to the frame200 with respect to the front-rear direction and the left-rightdirection. In this embodiment, the first side wall 205 a and the secondside wall 205 b constitute a third positioning portion 2051.

To the lower left stay 303A, the second supporting portion 313A is fixedin advance as described above. Accordingly, for example, by using thepositioning jig 400 described above, the positional adjustment (heightadjustment) of the supporting portions 311, 312 other than the secondsupporting portion 313 with respect to the up-down direction isperformed. Thereafter, the lower left stay 303A is fixed by welding tothe rear-side post 205 at fastening portions 251A to 254A and to therear-side plate 202 and the rear bottom stay 302 at fastening portions221A, 222A, 321A, 322A.

Also in such a case in this embodiment, the second supporting portion313A is prepared as the separate member from the lower left stay 303A.For this reason, similarly as in the First Embodiment, even when thedistance between the lower left stay 303A and the left-side is large,the formation of the projected portion can be easily made.

Other Embodiments

In the above-described embodiments, the respective stays constitutingthe bottom were fixed to the main assembly frame by welding, but mayalso be fixed by another fastening means such as a screw. This is alsotrue for the fixing between the supporting portions and the stays. Inthe above-described embodiments, the second supporting portion wasprepared as the separate member from the lower left stay, but may alsobe formed integrally with the lower left stay similarly as in the casesof the first supporting portion and the third supporting portion.

In the embodiments described above, the 3 stays were made movable in theup-down direction in the state in which the stays were positionedrelative to the main assembly frame with respect to the in-planedirection. However, in a state in which any one of the stays is madeimmovable relative to the main assembly frame in both of the in-planedirection and the up-down direction, other two stays may be made movablein the up-down direction in a state in which the two stays arepositioned with respect to the in-plane direction. For example, in theSecond Embodiment, the rear bottom stay 302 is fixed to the mainassembly frame 200 and then the lower front stay 301 and the lower leftstay 303 are moved in the up-down direction, so that heights of thefirst and second supporting portions 311, 313A may be made equal to theheight of the third supporting portion 312.

In the First Embodiment described above, the second supporting portion313 was made movable relative to the lower left stay 303 in the up-downdirection, and other supporting portions were provided integrally withthe associated stays. However, the three supporting portions may also beprepared as separate members from the associated stays so that the threesupporting portions are movable in the up-down direction similarly as inthe case of the second supporting portion 313. In this case, in a statein which the 3 stays are fixed to the main assembly frame, therespective supporting portions are disposed movably in the up-downdirection in a state in which the supporting portions are positionedrelative to the associated stays with respect to the in-plane direction.A constituent portion for positioning the first supporting portion 311movably relative to the lower front stay 301 in the up-down direction isa first stay-side positioning portion. A constituent portion forpositioning the third supporting portion 312 movably relative to therear bottom stay 302 in the up-down direction is a third stay-sidepositioning portion. A constituent portion for positioning the secondsupporting portion 313 movably relative to the lower left stay 303 inthe up-down direction is a second stay-side positioning portion. Then,after the height adjustment of the respective supporting portions, thesupporting portions are fixed to the associated stays by welding. Inthis case, in a state in which any one of the supporting portions isfixed to or integrally formed with the associated stay, other twosupporting portions may also be made movable in the up-down direction ina state in which the two supporting portions are positioned relative tothe associated stays with respect to the in-plane direction.

Further, of the 3 stays and the three supporting portions, one stay andone supporting portion are fixed to the main assembly frame, and othertwo stays and other two supporting portions may also be made movable inthe up-down direction. For example, in the First Embodiment, the rearbottom stay 302 is fixed to the main assembly frame 200, and then thelower front stay 301 is disposed movably in the up-down directionrelative to the main assembly frame 200. In this case, the firstpositioning portion 2040 and the second positioning portion 2050correspond to a main assembly-side positioning portion. Further, thesecond supporting portion 313 is disposed movably in the up-downdirection relative to the lower left stay 303. Then, heights of thefirst and second supporting portions 311, 313 may also be made equal tothe height of the third supporting portion 312.

In the above-described explanation, the so-called 3-point supportingstructure in which the number of positions of the supporting portionsfor supporting the image forming apparatus on the installation surfacewas 3 was described, but the present invention is also applicable to aconstitution, including 3 or more supporting portions, such as a 4-pointsupporting structure. For example, a constitution including three staysand four supporting portions will be considered. In this case, it isassumed that two supporting portions are provided on the same stay andother two supporting portions are provided on other two stays,respectively. Also in this case, similarly as in the above-describedexplanation, the respective stays or supporting portions are disposedmovably in the up-down direction in a state in which the stays orsupporting portions are positioned with respect to the in-planedirection, so that the height adjustment of the supporting portions canbe performed. For example, the supporting portions are fixed to theassociated stays in advance. At this time, the two supporting portionsare fixed on the same stay, and therefore a degree of a variation inpositional relationship of the two supporting portions with respect tothe up-down direction is small. Accordingly, when other two supportingportions fixed on other two stays are subjected to the height adjustmentrelative to the two supporting portions fixed on the same stay, avariation in positional relationship among the four supporting portionswith respect to the up-down direction can be suppressed.

Further, a constitution including 4 stays and four supporting portionswill be considered. In this case, it is assumed that the four supportingportions are fixed to the four stays separately. Also in this case, ofthe four stays, any two stays are in the same relationship as thatbetween the first stay and the second stay described above in therespective embodiments, so that the height adjustment can be madesimilarly as in the above-described embodiments. This is also true forthe case where the supporting portions are made movable in the up-downdirection relative to the stays.

The “supporting portion” referred to in the present invention includesnot only the case where the single supporting portion contacts theinstallation surface at a single contact portion as described above inthe embodiments but also the case where the single supporting portioncontacts the installation surface at two or more contact portions. Forexample, an interval between the two contact portions is made small toconstitute the single supporting portion. Here, in a constitutionincluding three supporting portions, when any one of the supportingportions contacts the installation surface at two contact portionsbetween which an interval is large, a resultant structure isconsequently not different from the 4-point supporting structure. Forthis reason, in this case, the interval between the two contact portionsis made small, for example, ⅓ of a length of the stay, with respect tothe arranging direction, on which the associated supporting portion isprovided.

According to the present invention, even when the bottom is constitutedby the plurality of stays, a variation in positional relationship amongthe supporting portions with respect to the up-down direction can besuppressed.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2015-001113 filed on Jan. 6, 2015, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A frame for forming an image forming apparatusfor forming an image on a recording material, said frame comprising: afirst stay, including a supporting portion for supporting said framerelative to an installation surface, for forming a bottom of said frame;a second stay, including a supporting portion for supporting said framerelative to the installation surface, for forming the bottom of saidframe; a post to which said first stay and said second stay are secured;and a positioning portion, provided as a part of said post, forpositioning said first stay and said second stay with respect to ahorizontal plane direction, wherein said first stay and said second stayare fixed to said post by welding.
 2. A frame according to claim 1,wherein said post is a first state to which one end of said first stayis fixed, and said developing portion is a first positioning portion,and wherein said frame further comprises a second post to which theother end of said first stay is fixed by welding and comprises a secondpositioning portion, provided on said second post, for positioning saidfirst stay with respect to the horizontal plane direction.
 3. A frameaccording to claim 1, wherein said frame includes a side plate.
 4. Aframe according to claim 3, wherein said first stay is provided in aside opposing a side where said side plate is provided in said frame. 5.A frame according to claim 3, wherein one end of said second stay isfixed to said post, and said positioning portion is a first positioningportion, and wherein the other end of said second stay is fixed to saidside plate by welding.
 6. A frame according to claim 3, wherein saidside plate includes a positioning portion for positioning said secondstay with respect to the horizontal plane direction.
 7. A frameaccording to claim 3, wherein said second stay is provided on a surfaceperpendicular to said side plate.
 8. A frame according to claim 3,further comprising a third stay, including a supporting portion forsupporting said frame relative to the installation surface andcomprising a third positioning portion for positioning said third staywith respect to the, wherein said third stay is fixed to said side plateby welding in a lower side of said side plate with respect to a verticaldirection.
 9. A frame according to claim 1, wherein the supportingportion of said second stay is fixed to said second stay by welding. 10.A frame according to claim 9, wherein said second stay includes a fourthpositioning portion for positioning the supporting portion of saidsecond stay with respect to the horizontal plane direction.
 11. A framefor forming an image forming apparatus for forming an image on arecording material, said frame comprising: a stay, including asupporting portion for supporting said frame relative to an installationsurface, for forming a bottom of said frame; a first post to which oneend of said stay is secured; a second post to which the other end ofsaid stay is secured; a first positioning portion, provided as a part ofsaid first post, for positioning said stay with respect to a horizontalplane direction; and a second positioning portion, provided as a part ofsaid second post, for positioning said stay with respect to thehorizontal plane direction, wherein said stay is fixed to said firstpost and said second post by welding.
 12. A frame according to claim 11,wherein said frame includes a side plate provided in a side opposingsaid stay.
 13. A frame according to claim 12, wherein said stay is afirst stay, wherein said frame includes a second stay, including asupporting portion for supporting said frame relative to theinstallation surface, for forming the bottom of said frame, and whereinone end of said second stay is fixed to said first post by welding, andthe other end of said second stay is fixed to said side plate bywelding.
 14. A frame according to claim 13, wherein said side plateincludes a positioning portion for positioning said second stay withrespect to the horizontal plane direction.
 15. A frame according toclaim 12, further comprising a third stay, including a supportingportion for supporting said frame relative to the installation surfaceand comprising a third positioning portion for positioning said thirdstay with respect to the horizontal plane direction, wherein said thirdstay is fixed to said side plate by welding in a lower side of said sideplate with respect to a vertical direction.
 16. A frame according toclaim 13, wherein the supporting portion of said second stay is fixed tosaid second stay by welding.
 17. A frame according to claim 16, whereinsaid second stay includes a fourth positioning portion for positioningthe supporting portion of said second stay with respect to thehorizontal plane direction.
 18. A manufacturing method of a frame for animage forming apparatus in which the frame includes a plate of staysprovided at a bottom thereof and said fixed to a main assembly frame andincludes at least three supporting portions, provided on the plate ofstays and in which of the plate of stays, a first stay is provided witha first supporting portion and a second stay is provided with a secondsupporting portion, said manufacturing method comprising: a first stepof disposing the first stay and the second stay relative to the mainassembly frame by moving the first stay and the second stay in avertical direction in a state in which the first stay and the secondstay are positioned relative to the main assembly frame with respect toa horizontal plane direction; a second step of performing positionaladjustment of the three supporting portions with respect to the verticaldirection by moving at least one of the first stay and the second stayin the vertical direction; and a third step of fixing the first stay andthe second stay to the frame by welding.
 19. A manufacturing method of aframe for an image forming apparatus in which the frame includes a plateof stays provided at a bottom thereof and said fixed to a main assemblyframe and includes at least three supporting portions, provided on theplate of stays and in which of the plate of stays, a first stay isprovided with a first supporting portion and a second stay is providedwith a second supporting portion, said manufacturing method comprising:a first step of disposing the first supporting portion relative to thefirst stay by moving the first supporting portion in a verticaldirection in a state in which the first supporting portion is positionedrelative to the first stay with respect to a horizontal plane directionand of disposing the second supporting portion relative to the secondstay by moving the second supporting portion in the vertical directionin a state in which the second support portion is positioned relative tothe second stay with respect to the horizontal plane direction; a secondstep of performing positional adjustment of the three supportingportions with respect to the vertical direction by moving at least oneof the first supporting portion and the second supporting portion in thevertical direction; and a third step of fixing the first supportingportion and the supporting portion to the first stay and the secondstay, respectively, by welding.
 20. A manufacturing method of a framefor an image forming apparatus in which the frame includes a plate ofstays provided at a bottom thereof and said fixed to a main assemblyframe and includes at least three supporting portions, provided on theplate of stays and in which of the plate of stays, a first stay isprovided with a first supporting portion and a second stay is providedwith a second supporting portion, said manufacturing method comprising:a first step of disposing the first stay relative to the main assemblyframe by moving the first supporting portion in a vertical direction ina state in which the first stay is positioned relative to the mainassembly frame with respect to a horizontal plane direction and ofdisposing the second supporting portion relative to the second stay bymoving the second supporting portion in the vertical direction in astate in which the second support portion is positioned relative to thesecond stay with respect to an in-plane direction; a second step ofperforming positional adjustment of the three supporting portions withrespect to the vertical direction by moving at least one of the firststay and the second supporting portion in the vertical direction; and athird step of fixing the first stay and the supporting portion to themain assembly frame and the second stay, respectively, by welding.